Question

what is the average time for the toy car to move 1.0 m on dirt?
20.2 s
24.4 s
28.1 s
60.7 s
time for toy car to travel 1.0 m on different surfaces

surface	time (s) trial 1	time (s) trial 2	time (s) trial 3
tile	29.1	26.7	28.5
cement	25.5	23.4	24.2

Explanation:

Step1: Recall average formula

The formula for the average (arithmetic - mean) of a set of numbers $x_1,x_2,x_3$ is $\bar{x}=\frac{x_1 + x_2+x_3}{3}$.

Step2: Identify data for dirt

For the dirt - surface, $x_1 = 20.0$, $x_2=19.2$, and $x_3 = 21.5$.

Step3: Calculate the sum

$x_1 + x_2+x_3=20.0 + 19.2+21.5=60.7$.

Step4: Calculate the average

$\bar{x}=\frac{60.7}{3}\approx20.2$.

Answer:

20.2 s